Lithography systems are used to manufacture semiconductor devices by exposing semiconductor wafers to specific patterns of light. This is typically done by shining light, through a patterned reticle, onto the wafers. A reticle is supported within a reticle stage, which is in turn supported by a frame. The reticle stage is supported in a way that it can be precisely moved with respect to the frame and thereby with respect to the wafer. The reticle stage can be supported through mechanical devices such as actuators or through resistance-free techniques that employ air pressure or electromagnetic forces. In some lithography systems, a wafer stage, which supports a wafer, can also be precisely moved with respect to a supporting frame.
The reticle or wafer stages require one or more utilities, such as electrical power, electrical control signals, fluids (e.g., for cooling purposes), and gases (e.g., to function as a conductor) to function. Such utilities are usually transferred to and from a stage through flexible cables and hoses. Usually, the utilities are transferred between the stage and the supporting frame. Unfortunately, typical problems with such transfer techniques include vibration transmission between the stage and the frame, particle generation by the connecting hoses and cables, and leaks by the hoses and cables. Vibration transmission occurs because the cables and hoses provide a vibration path between the stage and the frame. This causes a reduction in stage positioning performance. Also, cables and hoses can be caused to vibrate if a natural mode of the cables and hoses is excited either by the stage motion or by the base motion. Particle generation is problematic because moving cables and hoses can generate particles as they bend, flex, and rub on fixed surfaces. These particles can reduce performance of lithographic processes if they should migrate to the reticle, optics, wafer, or metrology devices. Finally, leakage is always a risk since flexible hoses can break.
The solutions to reduce risk of such problems have led to stiff, bulky, or high bend-radius cables and hoses, which consume space or worsen vibration transmission. Other solutions to reduce these risks include limiting coolant material to one, which is less effective than water, but evaporates quickly and is non-corrosive to system components.
These problems are especially problematic with Next Generation Lithography (NGL) systems, which require extremely high tolerances. One type of NGL system is an Extreme Ultraviolet (EUV) system, which operates in a vacuum and utilizes specially coated mirror optics. Reticles in EUV systems are supported on one side of a chuck, which is attached to the reticle stage, so that light from the light source can be reflected off of the reticle. In addition to the already discussed problems, EUV systems have additional problems that are associated with flexible cables and hoses. For one, out gassing of water and hydrocarbons from the flexible hoses can have adverse affects on the life of optical elements. For example, water can corrode optical elements and such damage is irreparable. Also, hydrocarbons reduce optical reflectivity over time, which will reduce system throughput. Out gassing also adversely affects the time to reach operating vacuum levels. The possible solution of baking-out cables and hoses only makes them stiffer which in turn exacerbates certain problems.
In view of the foregoing, techniques for transferring utilities to a reticle or wafer stage without accompanying physical disturbances or contaminating particles or gases would be desirable.